A little about my house in Texas and a shameless plug for my clean energy blog (gotta build those Google links). It was built in the 80's. Single pane windows. I'm not sure how good the insulation is, but I think the roof needs to be replaced in a few years. When that happens, we will definitely go solar.

We're running about $100/mo on our utilities now (gas, water, electric, waste) which is not bad. That will jump up in the summer, though.

I think we've done the easy efficiency things... (LED bulbs, efficient AC & appliances, bubblewrapped fridge, plugged drafts).. but I am interested in your ideas. The blog talks about how we've put heavy curtains up instead of replacing the single-pane windows. It was a lot cheaper and easier, so we're pretty happy with that. Eventually we'll do the window replacement, too, but I expect it to cost several thousand bucks.

Well, I can see your point that plugging holes might be more cost-effective, but I still think I should go solar immediately since the return is (+) and there would be no cost to me. Ideally, I would do both immediately!

But to answer your questions, we pay 8c/kWh, net metering reimburses at 9c/kWh. The AC is a Goodman (15 SEER) and the furnace is an older Payne that I don't see a model number on.

How do you mean that PV is at "no cost"? I certainly hope you don't consider Solar City to be "no cost".

There are a lot of consequences to "renting" a PV system. Examine carefully before you bite.

Conversely, the cost of a DIY self install grid connected system is about $1.25 a watt. Then YOU get the 30% tax credit. A 10 kW system for roof (forty, 250 watt panels) would cost you about $12,500. Then the tax credit gives you back cash $3750 for a net cost of $8750. You now get 100% of the kWs from this system.

When you "rent" from Solar City, they get the 30% tax credit and they get most of the kwatts. You get a slightly discounted rate for your power consumption.

Maybe you are thinking of a loan of some sort to finance a PV system.

You may not need a 10 kW system. Half that may be great for you. Look at your bills to figure out your kWhr peak use (likely July - August) and plan from there.

I would, at a minimum, get double pane windows and check attic insulation (increase to R40). Per dollar spent, even with loans, conservation in a home like yours beats out PV every time when you look at return on investment.

Lastly, is your roof orientation (angle to south) appropriate for a PV system?

Think of this home energy thing more as a long-term investment, and you will be better off from the get-go. Having a blower door test done, doing a manual j analysis, getting some thermal images, and the like are all preliminary steps that fit into your energy budgeting plan. Insulation is one of those aspects that reaches beyond return on investment. Although it has a diminishing rate of return, it will alter your home comfort levels in a dramatic and permanent fashion. Doing it first will reduce all your subsequent needs and has a compound effect on the whole budget and project.

I can't tell you how many people I've helped with these projects that wanted to just throw equipment at their homes in the beginning. Big fans, windows and doors, climate controls, strange roofing and insulating materials, the list just goes on forever. Most of these homeowners began with a "one thing at a time" mentality, not putting much thought about the improvement of the home as a combined project. Obviously, you have done a few of these projects, and they have added up to a tangible sum. I encourage you to step back and do a decent audit and at least do some math before you make any major investment in equipment or labor hours.

Consider this:

A thermal camera on a cold day has changed a whole lot of people's minds. That 75 bucks saved them thousands in about fifteen minutes. For some odd reason, their old windows are never good enough after seeing all that red and yellow on the screen...

I would say that a home energy audit is the most important thing you could do, even if you have to pay out of pocket for it. FWIW, I spent $600.00 to have an audit and because of that, I added a bit of extra insulation in my attic and put in a 2 ton HVAC system instead of the HVAC "experts" suggested 3.5 to 4.0 ton unit. {I had 4 quotes, 3 = 3.5 ton, 1 = 4.0 ton using "the rule of thumb" as nobody would do a Manual J}

The $600.00 was saved in the cost of the new unit, plus I found out where the couple of minor improvements needed to be made. Some of what I planned to do turned out to be non-issues.

Good luck with whatever your plans are for making your home more energy efficient. In most cases, lowering your utility bills through efficiency comes with the REAL benefit of a more comfortable home to live in.

Single pane windows...build storm windows for those months you don't open your windows. I built mine out of plexiglass mounted to the back of wooden frames. They help with drafts, infiltration and sound of neighbor's dogs too. I'd put some solar screens on your windows to, solar screen is cheap and easy. Windy winter days are good for finding air leaks around your house. check around plumbing penetrations, outlets, doors, window casing, baseboards etc. You'll be surprised where everything leaks.
If you have a gas furnace in an interior closet make sure its sealed and has a combustion fresh air intake from outside. Otherwise as your furnace burns it uses conditioned air while your house sucks in cold air from outside.